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My brother and I are restoring an old Grumman Kurbwatt electric car and as you can probably guess it's not easy to find info about them online and we're currently trying to chase a dead short that we suspect is somewhere in the motor controller (we're getting continuity between the 3 main posts coming off of it and we assume we shouldn't be) and was hoping someone might know more about this or if where I could and try to find a replacement controller if we had to go down that road.
Thanks Amon Little
120176
 

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It's measuring milliohms (it automatically measured as such)
Thanks I'll have to look that over, wish I was better at deciphering that stuff
 

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Looking at the schematic, there's a big capacitor bank and 2 diodes between B+ and B-, then all sorts of complex power stage parts (transistors etc). Can you look at the capacitors and see if they've exploded? I wouldn't be at all surprised if they were dead after ~40 years.
Do you need to keep the original controller?
 

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We didn't see any obvious capacitors that were blown but thats definitely a possibility, do you think I'd be able to do a continuity test on the capacitors to see if they're no longer functional (they're pretty big capacitors).
And not really if you or some else might know of a controller that would be an okay substitute we'd be comfortable doing that too I think.
And thanks if you need any other pictures I'll add them.
 

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We didn't see any obvious capacitors that were blown but thats definitely a possibility, do you think I'd be able to do a continuity test on the capacitors to see if they're no longer functional (they're pretty big capacitors).
And not really if you or some else might know of a controller that would be an okay substitute we'd be comfortable doing that too I think.
And thanks if you need any other pictures I'll add them.
 

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If you could disassemble the controller you could do a continuity test - rising resistance, going eventually out of range, means good.
Pictures would be helpful just so I can see what's going on inside.

I used to be able to recommend a Curtis controller, but now that everyone has moved to AC motors it's harder to source DC controllers.
If you're up for a real fun project you could get a Prius motor controller, take out the power stage, and use an Arduino or similar to create PWM. Then for ~$150 you'd have a nice powerful (350A) controller.
 

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120178

Top down view and a couple of the capacitors, that does sound interesting with the prius controller is that something you've done before?
 

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Well... It looks fine... I can't really say much more. I guess you can take off the caps and see if it still measures the same way.
I haven't used the Prius controller myself but some users on OpenInverter published circuitry to do it relatively easily. If you go over to that forum you can ask about the controller, maybe purchase a board from somebody. Prius Gen2 Inverter DC Motor Controller - openinverter forum
-Isaac
 

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My brother and I are restoring an old Grumman Kurbwatt electric car and as you can probably guess it's not easy to find info about them online and we're currently trying to chase a dead short that we suspect is somewhere in the motor controller (we're getting continuity between the 3 main posts coming off of it and we assume we shouldn't be) and was hoping someone might know more about this or if where I could and try to find a replacement controller if we had to go down that road.
Thanks Amon Little View attachment 120176
What reading do you get when you reverse the leads? I recommend you switch your meter to the diode test position and check all transistors for shorts. (Are you absolutely sure that the M is milleohms? As I remember that meter m is milleohms and M is meg ohms) The most common failure of controllers is the transistor switches. Most often they fail shorted.
 
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